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LAN & WAN Basics

Introduction

8/20/2008: Corrected system info

Many things have changed since the first version of this tutorial was written in 2003. Computers and their internal busses have gotten a lot faster and file sizes have gotten a lot larger. But oddly enough, gigabit LAN ports have not become standard in consumer networking gear. Notebooks may come with the latest draft 802.11n wireless. But they may also come with only a 10/100 Ethernet port.

So consumers are left on their own to determine whether to shell out the additional cost to move to an all gigabit network. This Need To Know is aimed at helping you make that decision.

What is Gigabit Ethernet?

Gigabit Ethernet, also known as "gigabit-Ethernet-over-copper" or 1000Base-T, is simply a version of Ethernet that runs at speeds up to 1,000 Megabits per second, i.e. 10 times faster than 100Base-T.

The ruling IEEE standard for gigabit Ethernet, 802.3z, was approved in 1998, but it wasn't until June 1999 that the 1000BASE-T standard (IEEE 802.3 Ethernet Standard for Gigabit Ethernet on Category 5 copper) was approved. It was this standard that moved gigabit Ethernet out of the server rooms and backbone closets and enabled it to be run pretty much anywhere that 10/100 Ethernet is run today.

Before 1000Base-T, gigabit Ethernet required using either fiber-optic or special shielded copper cables, neither of which was practical for everyday LAN construction. These versions (1000Base-SX, 1000Base-LX, and 1000Base-CX) are still in use today in specialized applications, but we won't be focusing on them in this article.

The 802.3z Gigabit Ethernet task did their work well, and were able to come up with a standard that is, for all intents and purposes, a ten times faster version of 100Base-T. 1000Base-T was also designed so that it is backward-compatible with 10/100 equipment, and uses CAT-5 (or better) wiring (the stuff that you're using for your current LAN).

Do I Need it?

Most of the early sales literature for gigabit Ethernet contained pitches focused on the "enterprise" market, and usually aimed at the data center manager. Since gigabit Ethernet provides a 10 times larger "pipe" for data flow than 100Base-T, the natural first applications were at the points of highest bandwidth need. Server-to-server, switch-to-switch, and "backbone" applications were all named as candidates for gigabit Ethernet, and there are white papers and case studies a' plenty to show that gigabit Ethernet is a good investment in these cases.

As gigabit gear prices have followed their natural downward march, vendor pitches have widened to include gigabit deployment to desktop machines of "power users" and workgroups with "bandwidth intensive applications".

Since some small networks' data needs are much more modest, it's fair to ask whether a small network would ever need the capacity that a 1000Base-T network provides. Let's look at some of the applications that are commonly used in a small network and see if they need what gigabit Ethernet can provide:

Gaming
Since most networked games are designed for over-the-Internet play, they're pretty smart about the amount of data they send across the network. The games rely on local processing power for the heavy lifting and send only what they have to across the network, so that they are playable under the wide range of network conditions encountered on the Internet.
Although in gaming, faster is always supposed to be better, gigabit Ethernet won't provide any advantage in networked frag-a-thons. Response time is the important factor for networked gaming, but anything much below 10ms doesn't provide any advantage, and you'll get that from even a 10Base-T network. So, again, gigabit Ethernet's extra capacity will just be wasted for this application.

Streaming video
This is one area where the requirements have changed since 2003 and continue to evolve. Two forces are at work and are pulling in opposite directions.

IPTV (Internet Protocol Television) has been a big force in Europe where telcos are moving into providing TV service. The target bandwidth requirement is around 5 Mbps for standard definition programming. YouTube and other web-based video, including all the major U.S. broadcast networks, are also competing for eyeballs. Bandwidth requirements vary due to a wide range of formats and distribution methods.

But since these services are trying to reach the widest audiences through the relatively slow connections that pass as "broadband" in the U.S., bandwidth requirements are again kept low. 3 - 5 Mbps is again the sweet spot, with smaller picture formats using even less bandwidth. Most of the content is standard definition, with only a few sites experimenting with streaming "high definition" content.

Pulling in the other direction is the move to High Definition TV that will culminate in the U.S. broadcast switchover in February 2009. As demonstrated in HD Streaming Smackdown: Draft 11n vs. Powerline, even 720p with very efficient H.264 encoding has bandwidth peaks commonly over 20 Mbps. True 1080p streams would average closer to 20 Mbps, with peaks into the 30s.

The net result is that, unless you're a video production house, or have the need to provide more than four or so simultaneous HDTV streams, a 100Mbps LAN will handle streaming video just fine.

TIP: See this article for a good description of the bandwidth requirements of the popular MPEG standards.

Moving large files across the network
This requirement used to be more often encountered in a small-office situation, especially in graphic-design houses, architectural firms, and other businesses that routinely deal with file sizes in the 100 MB to multi-GB range. But with a growing number of consumers building large video libraries through DVD ripping and P2P filesharing, folders in the tens to hundreds of gigabytes are becoming more common.

Although a quick cut at the math would have you think that a 100 MB file would take only 8 seconds to move across a 100 Mbps network [ (100MByte X 8 bits/Byte) / 100Mbits/sec ], in reality, many factors conspire to make the actual transfer time much longer. Some of the factors that come into play are OS used, applications you're running, amount of memory in your machines, and their processor speed and age. (The age is an indicator of motherboard bus rates.)

Thegood news is that modern computers and LAN cards can achieve close to 100 Mbps "wire speed" throughput. But once again, operating systems can slow things down significantly, increasing "drag and drop" file transfer times significantly.

Fortunately, moving large files is something that gigabit Ethernet can really help with, although you won't see a 10X improvement!

Network backup
This can be thought of as a variant of the "large files" case. If your LAN is set up to back up all its machines to one system that acts as a fileserver, a gigabit LAN can help speed the process. However, this is another case in which widening the "pipe" to the backup server may have no effect if the server (and especially the backup medium) can't keep up with the incoming flood of data.

If this is your application, you'll need a speedy server with plenty of memory, and be backing up to a fast hard drive, not tape or CDROM, in addition to upgrading your network to gigabit.

Server based applications
Another scenario more likely to be encountered in a small business vs. a home LAN is one in which a lot of data frequently moves between a client and server due to a server-based application. But again, you need to analyze the amount of network data to see whether "a lot" would be enough to see an improvement from a switch to gigabit speeds.

But let's say that you're still not ready to buy, but don't want to rule out the possibility of an upgrade in a year or two. Is there anything that you need to do now to prepare? The next section will examine what you need to do for what is frequently the most expensive, and hardest to change part of your network - the cabling.